The present invention relates to a recording method for forming a visible image on a recording sheet by a magnetic brushing process using a dry developing powder, and, more particularly, to a recording method for forming a picture image directly on a recording sheet in response to an input signal rather than by forming an optical image directly on the recording sheet surface.
There are known method for electronic photographing, and electrostatic recording or electrostatic printing for duplicating documents or drawings. These duplicating methods employ inorganic photosensitive materials such as, for example, selenium, zinc oxide, cadmium sulfide, covered with an insulating film, or organic photosensitive materials such as, for example, polyvinylcarbazole, poly-N-vinyl-carbazole, and picture carriers such as, for example, a high resistance polyester sheet and an electrostatic recording paper formed of a low-resistance base on which a dielectric is formed. The surface of the carrier is uniformly charged with electricity and then exposed to light, or needle electrodes are brought into contact with the dielectric surface and supplied with a signal voltage to form an electric latent image. Then, a developing agent powder containing a magnetic substance is used to develop the latent image by a magnetic brushing process, and, subsequently, the image is fixed as, or fixed after the developing toner image is transferred onto a transfer sheet such as an ordinary paper, to form a final picture image. Duplicating methods of this type need a latent image forming means in addition to the developing means; therefore, the apparatus needed for duplication is very complicated and of a large-size.
Therefore, generally in a printer unit used as terminal equipment for computers and facsimile machines, a so-called direct recording method for reproducing characters, pictures, etc. has been proposed wherein the image is reproduced directly on the recording sheet as a visible image not by forming direct latent images. For example, in Japanese Patent Publication No. 30228/80 corresponding to U.S. Pat. No. 3,816,840, a dielectric recording member is disposed between a pair of electrodes, a conductive toner is deposited on the first electrode to form a conductive path between the electrode and the surface of the recording member, and then the toner is selectively deposited on the surface of the recording member in accordance with a potential signal applied between the electrodes. In, for example, U.S. Pat. Nos. 3,914,771 and 3,946,402, a conductive magnetic toner, retained on a cylindrical shell, is moved by the rotation of a magnetic roller within the shell, and electric pulses are applied to the electrode needles in synchronism with the rotation of the magnetic roller, in which recording method a toner applicator is used. Moreover, in the Japanese Patent Laid-open Application No. 127578/80, a permanent magnet is mounted on the needle electrode to establish a magnetic field at its tip end in an attempt to solve the problems encountered in the methods of the last-mentioned U.S. Patents.
In most of the conventional direct recording methods, a recording member is passed through a recording region formed between the recording electrode and an oppositely disposed electrode, with an electric field, based on a picture signal, being established between the electrode, or a magnetic field being superimposed upon the electric field so as to cause the magnetic toner, retained on the opposite electrode, to be selectively deposited on the recording member. A disadvantage of these proposed methods resides in the fact that, to obtain a high quality picture image, it is necessary to strictly specify various conditions such as, for example, the gap between the electrodes, the amount of toner, and an adjustment of the developing conditions in accordance with the environmental condition because, when an ordinary paper of volume resistivity of less than 10.sup.12 .OMEGA..cm is used as a recording paper, the surface resistance of the paper is greatly changed by environmental conditions such as humidity, temperature, etc. Additionally, with these conventional direct recording methods, a high recording rate is impossible.